It is intended to investigate the properties of the sensitized T-cells that mediate immunity to the Meth A fibrosarcoma in syngeneic BALB/c mice. Mice that have completely regressed their meth a tumors in response to endotoxin administration, and which consequently are specifically immune to a Meth A challenge implant will serve as a source of mediator T-cells. The method of adoptive immunization will be employed to determine the distribution of these T-cells in the immunized donor and their distribution and functional life span in the adoptively immunized recipient. Anti-Ly antisera will be employed to preferentially delete subpopulations of donor T-cells according to their Ly surface antigens. This will determine whether the T-cells that mediate immunity to tumor syngrafts are Ly 1 ion 2 ion, as are the T-cells that express immunity to tumor allografts. Adoptive immunization will be employed to determine the kinetics of generation of mediator T-cells in the draining lymph nodes and spleens of mice whose tumors are regressing in response to endotoxin therapy. An attempt will be made to concentrate these mediator T-cells in peritoneal inflammatory exudates with a view to purifying them for additional functional studies.